Method of forming a round collagen strand



Dec. 17, 1963 E. J. GRlsET, JR

METHODMOF4 FORMING A ROUND COLLAGEN STRAND Original Filed April13,-'1'959 4 Sheets-Sheet 1 Y @M Mgg Dec. 17, 1963 E. J. GRISE-T, JR3,114,235

METHOD oF FDRMING A ROUND coLLAGEN STRAND original Filed April 13, 19594 sheets-sheet 2 INVENToR. CP/V537- Z' 3P/:57k

,4 7' TUR/VE Y Dec. 17, 1963 E. J. GRlsET, JR

METHOD OF FORMING A ROUND COLLAGEN STRAND Original Filed April 13, 19594 she'ets-sheet s QM u) ,4 T TOR/VN Dec. 17, 1963 E.; GRlsET, JR

METHOD 0F' FORMING A ROUND COLLAGEN STRAND OriginalFiled April 13, 19594 Sheets-Sheet 4 INVENTOR.

United States Patent yO 3,114,235 METHD F FGRMI-NG A ROUND COLLAGENSTRAND Ernest J. Griset, Jr., Bound Brook, NJ assigner to Ethicon, lne.,a corporatonof New Jersey @riginal application Apr. 13, 1959, Ser. No.806,067. Divided and this application Dec. 1, 1960, Ser. No.

4 Claims. (Cl. 57-157) swollen in acid solution to a diameter of about200 to I 2G00 Angstrom'units.

The term monoilament, as used herein, means a single thread of orientedcollagen fibrils as extruded through a single orifice in a spinnerette.

The term multilament, as used herein, means a group of individualseparate filaments or incompletely bonded filaments that have beenextruded through a spinnerette.

rEhe term Vopen multilament as used herein means a fluffy multilainent,the bull; of which is large due to the separation of adjacentmonoiilaments.

The term ribbon, as used herein, means a thin film of oriented collagenfibrils, for example, as extruded through a slit.

The term multiribbom as used herein, means a group of individual ribbonsextruded through a plurality of slits. s

The term strand, as used herein, means a group of filaments or ribbonsthat have been united to form a bonded structure.

The termv cord, as used herein, means a group of filaments or ribbonsthat have been twisted together and re bonded or partially bonded.

Practically the entire production of absorbable sutures and ligatures iscurrently made from sheep or beef gut by a process that isV timeconsuming and expensive, and yet is not adapted to produce a uniformiproduct. The percent of ,production that is rejected, therefore, forsome defect such as lack of tensile strength or lack of uniformity, islarge. The starting material, e.g., sheep intestines, is available onlyin limited quantities and one i can notpredetermine the exact size ofthe finished product.

In view of the obvious deficiencies of such surgical catgut and thedisadvantages of the ,present method of manufacture, many attempts havebeen made to obtain a better product by treating collagen to form aswollen fibrous mass that is extruded into a dehydrating bath. It hasbeen found necessary to stretch the extruded collagen to orient it asunoriented collagen lacks the strength that is required of a suture.xtruded collagen is quite fragile asit leaves the dehydrating bath andoften breaks upon stretching. In addition, the tensiony causes theextruded collagen to flatten and become deformed through Contact withthe godets of the spinning machine unless eps are taken to prevent this.

It is an object of the present invention, therefore, to stretch anextruded collagen multililament or multiribbon without breaking it.

It is also an object of this invention to prepare a round Mice collagenstrand or cord that is of uniform cross-section throughout its length.

lt is another object of the present invention to vcontrol the amount ofmoisture in an extruded collagen multifilament, multiribbon, strand orcord.

till another object of the present invention is to produce a cord ofcollagen multilament or multiribbon.

I have now discovered a method of subjecting a continuously moving wetcollagen multiilament, ribbon, multiribbon or strand to a wringingaction, whereby the amount of moisture in the collagen is controlled. Ido this by the use of a device called a false twister that automaticallyimparts a false twist to the strand. A false twist may be defined as atwist whose direction on one side of a point of contact is reversed onthe opposite side, lthus cancelling the twist. By varying the speed ofthe false twister, I can adjust the moisture in the collagenmultilament, ribbon, multiribbon or strand and thereby the tensionduring the spinning process. The mount of moisture that is present inthe extruded collagen is quite important, as moisture decreases thetensile strength so that a wet collagen product can not 'oe stretchedSullicientiy without breaking.

ln addition, twisting a collagen multiiilament, ribbon, multiribbon orstrand as it leaves the dehydrating bath increases the strength of themoving collagen at the place where it is weakest.

The method of operating the false twister may be varied in accordancewith the present invention to achieve dierent results. Thus, the speedof the false twister is one of the spinning conditions that determinesthe extent to which the multiiilament is united to form a strand. If thefalse twister rotates slowly in a humid atmosphere, a strand isobtained, but the dryer the atmosphere, the less the tendency to bond.It it rotates rapidly in a moist atmosphere, the tendency not to bond,which results from the rapid rotation, is compensated for by themoisture and bonding is achieved.

The invention #will Iapps-ar `more cleanly from the follorvving detaileddescription when t-alten in connection with fthe `accompanying drawings,which show, by way of example, a preferred embodiment of the invent-iveidea.

Referring now to the drawings,

FIGURE ll is 'a schematic View of the one form of spinning machine thatmaybe used in the manufacture of Icontinuous collagen mlultiflarnents orstnands.

FIGURE 2 isa perspective view of a false twisterwhich is used to wiringmoisture out of the inultila-ment and to round the strand during thespinning proces-s.

FlGURE `3 is another perspective view of the false twister of FlGURE 2i.

FIGURE 4 is la sectional view of the false twister illustnated in FlGURE3.

FlGURE 5 is .a perspective view of an improved false twister.

FIGURE 6 is `a sectional view of the false twister illustrated in FIGURE5 showing a gear driving means.

Throughout the present specification, collagen multifilament that istraveling from the spinnere-tte, through the spinning column, over theidler pulley 137, around guide 138, and prior to contact with godetltlsl, will be referred to as in the extrusion 1st-age.

Collagen multililarnent, or strand, that is traveling betwt-:env godetlill land idler pulley 139, and prior to contact with godet 1h21, willtbe referred to as in .the first stretching stage.

Collagen multililarnent, strand or cord that is traveling between godet102, `around the idler pulleys and 136, and prior to contact with godetltl, will Ibe referred -to as in the second stretching st-age.

Referring now to FGURE l of the dra-Wings, which villustrates avertically upward spinning machine, there are three godets $101, 102 and103, of equal circumference (about 3 inches), and they may lbe made ofnylon. It will Ibe noted that the collagen dispersion in a reservoir 114is maintained under a pressure that is continuously indicated by a gauge141. This dispersion is forced by a pump 115 througgh homogenizing jets116 and 117' and a filter and is extnuded vertically upward through arecirculating dehydrating bath 145, over an idler pulley 137, around aguide 13S Vand onto godet 101. The extruded collagen is pulledvertically upward out of the bath by godet 101.

The extruded collagen 146, as it leaves the dehydrating bath 14S andpasses through the extrusion stage, is quite moist, so that there isvery little tension between the idler pulley 137 and the guide 138.

The collagen multifilament is wrapped three times around godet 101before passing to the first stretching stage. Three wraps are sufficientto prevent slippage because the collagen is wet as it reaches thispoint. At the end of the first stretching stage, however, the collagenis comparatively dry, so that about twelve wraps around the godet 102are required to prevent slippage.

In the first stretching stage, a false twister 112 twists the collagenmultifilament as it leaves godet 101, and thus improves the tensilestrength throughout the portion of the multilament extending from thetop of the false twister 112 to the godet 101. It is this section of theextruded collagen that is most weak because of occluded moisture, andthe twist imparted by the false twister 112 prevents breaks that wouldotherwise occur as the collagen multifilament leaves the godet 101. Thefalse twister 112 also wrings the moisture out of the multifilament and,together with a heater 133, controls the moisture content of thecollagen multifilament.

In the first stretching stage, the collagen multifilament may bepartially rounded and partially bonded by the false twister to form astrand. The amount of bonding that occurs in the first stretching stagemay be increased by wetting out the multifilament at godet 101 withwater and operating in a moist atmosphere (between 30 and 60 grains ofmoisture per pound of dry air). It is customary, however, to spin in adry atmosphere (less than 20 grains of moisture per pound of dry air),and, under these conditions, there is little or no bonding of thecollagen multifilament in the first stretching stage.

As pointed out above, the speed of the false twister 112 controls theamount of moisture in the collagen multifilament, and thereby effectsthe tension as registered by a tensiometer 142 and the amount of stretchthat may be applied without breaking the strand. The speed at which thefalse twister is operated depends upon the relative humidity of thespinning atmosphere, the size (cross-sectional area) of the collagenmultifilament or strand, and the character of the collagen dispersion.

I have noted that increasing the speed of the false twister tends toreduce the amount of bonding and a dry open multitilament is collectedon godet 102 if the moisture content of the atmosphere is kept low.

On the other hand, operating the false twister at a slower speed willresult in partial or complete bonding if the multifilament or atmosphereis moist.

The stretch imparted between godets 101 and 102 provides orientation ofthe drying multifilament or strand and improves the tensile strength.

When the false twisters 112 and 113 are operated properly, spinningconditions may be controlled so that godet 101 is operated at l0 rpm.,godet 102 is operated at 14 rpm., and godet 103 at 15 r.p.m. Under theseconditions, one would obtain, in addition to the 40% stretch betweengodets 101 and 102, another 10% stretch between godets 102 and 103. Theover-all stretch is preferably varied from about 20% to 50%. Since theoptimum amount of stretch will result in maximum strength, the machineis preferably operated to give a CII stretch somewhat less than thatrequired to break the filaments of the strand.

ln the second stretching stage, the moving multifilament or strand iscontinuously washed and/ or tanned by contact with a downward flow oftanning solution 144 in a direction opposite to the direction of strandtravel. The wetted out strand from a freely rotating idler pulley 132 isreturned to an idler pulley and contacts the tanning bath a second time.In its wet condition, the tanned strand is stretched an additional 10%by the more rapidly rotating godet 103.

The problem in the second stretching stage is to completely bond themultifilament to form a strand that is round. Multiple passages over thecircular godet surfaces, especially when the filaments are undertension, forms a attened strand. The deformation takes place mostreadily when the strand is wettest, as it leaves the spin bath andtanning bath. Moisture, however, is required to bond together thecollagen filaments to form a unitary strand.

1n the practice of the present invention, this problem has been solvedby using a false twister 113 to place a twist in the strand. The twistbacks up to the idler pulley and as the wet strand emerges from it, agradual tapering takes place which rounds the strand and wrings out themoisture. By locating the idler pulley 135 a sutiicient distance abovethe false twister 113 (preferably about 4 feet) so that the strand isquite dry when it contacts the false twister, I have found that theroundness may be permanently bonded into the strand and is not removedas the resulting cord passes below the false twister. If necessary, aheater 134 may be directed to dry the strand below the false twister andpermanently set the uniform circular cross-section that ischaracteristic of the strand above the false twister 113. The wringingaction during the formation of the twist assists in drying the strand.

A preferred type of false twister characterized by three idler pulleysrotating in a common plane, is illustrated in FIGURES 5 and 6 of thedrawings.

In these figures, 1 represents the twister head, 2 the hollow verticaldrive shaft, 3 the horizontal drive shaft, 4 ball bearings for the shaft3, 5 ball bearings for the shaft 2, 6 the bevel gear fixed to thehorizontal shaft 3, 7 the hollow bevel gear fixed to the shaft 2, 8 and9 the small rollers, 13 the axis of roller 10, 11 and 12 the axes ofrollers 8 and 9, 10 the large roller, 14 the multifilament, ribbon,multiribbon or strand, and 15 is one of several set screws that fix thetwister head 1 to the hollow vertical drive shaft 2.

The arrows in FIGURE 5 indicate the relative motion of the multifilamentand the twister head. It has been found advantageous to allow themultifilament to traverse the false twist mechanism in the directionindicated, since in such use, it passes in a highly twisted conditionthrough the hollow bore of the vertical shaft 2.

The central guidance of the multifilament is obtained by placing therollers 3 and 9 on their axes 11 and 12 at right angles with the axis ofrotation of the vertical shaft 2 in such a manner that the perimeter ofeach roller is approximately tangential to the axis of rotation of thevertical shaft.

The large roller 10 is disposed between the rollers 8 and 9 on the axis13, which is parallel with the axes 11 and 12 but offset therefrom. Thusthe rollers 8, 9 and 10 rotate in a common plane, but the position anddiameter of the roller 10 is so chosen that the path of travel of themultilament 14 deviates at roll 10 from straight line travel along theaxis of rotation of shaft 2 by a distance of the order of 1/2 inch. Thedimensions of the rollers 8, 9 and 10 and the eccentricity of the axis13 are not critical as it is only necessary to provide suflicientfrictional engagement of the multitilament 14 to twist the same when thetwister head 1 is rotated. FIGURES 2 through 4 illustrate an alternatetype of false twister that may be used in the practice of the presentinvention. The false twister of FIGURE 2 is air driven by a jet of airfrom the nozzle 16, which is intercepted by the vanes 17, therebycausing rotation of the gear 18. This gear 18 meshes with the upperflange 19 of the false twister 20 and causes rotation thereof in thedirection shown.

As indicated in FIGURE 3, the false twister may be constructed with aslot 21 extending from the centralfopening and vertical axis of thetwister 22 to the circumference of the twister head 23. This slotfacilitates threading the false twister in the event that the collagenstrand breaks during processing.

The preferred shape of the roller 24 is best shown in FIGURE 4. Theconical taper from the inner flange 25 of the roller 24 to the outeriiange 26 minimizes abrasion of the collagen strand as it passes throughthe false twister.

The operation of the false twisting device perse and in conjunction withthe procedures applied to collagen multiilarnents is believed to beapparent from the `foregoing description and no further eiucidation isdeemed necessary as those skilled in the art will now understand how thefalse twister operates. It will also be understood by those skilled inthe art that the false twister will operate to round and dry not onlycollagen multilamentbut also collagen ribbon and collagen multiribbon.

The false twister illustrated in FIGURE 5 is particularly well adaptedto the manufacture of round collagen strands from collagen multiilamentaccording to the spinning scheme illustrated in FIGURE 1. For thisparticular use, when the rate of spinning is aboutV 30-50 inches perminute, the false twisters may be rotated aboutlOO r.p.n1. to 1G00 rpm.When spinning a size 5/0 strand, both false twisters may be operated atabout 600-900 r.p.m. During the manufacture of a larger strand (size2/0), the speed of both false twisters is preferably reduced to about400 rpm. As mentioned above, the speed of the false twisters may bevaried to compensate for spinning conditions. If bonding is obtained,when an open multifilament is desired, the speed of the'false twistersmay be increased. Slower rotation of the false twisters provides thebest conditions for bonding and rounding the strand.

The tensiorneters 142 and 143 shown in FIGURE 1 measure tension placedon the dry multilament strand by godets 102 and 163. The tensioneffected by godet 102 varies from to 300 grams with the humidity,temperature, speed of the false twister and other operating conditions.These operating variables are preferably adjusted to spin with a tensionof between 75 and 150 grams. The tension on the dry strand effected bygodet 1% is between 200 and 500 grams. The dried strand is removed fromgodet 103 by the takeup spool at approximate.y 45 inches per minute.

It has been observed that atmospheric humidity, a variable during thespinning of a strand, plays an irnportant part in the stretch, the iinaltensilestrength and the bonding of the col-lagen multifilament to form astrand. if the atmospheric humidity is sufficiently low, an openmultilament may be collected. The humidity is preferably controlled byencasing the spinning operation within the smallest practical enclosure.Air lof controlled humidity is introduced into this enclosure to replacethe humidity of the building atmosphere wlith the humidity of acompressed air system. Superior bonded strands are spun when thehumidity -is controlled between 3() and 60 lgrains of moisture per poundof ydry air. Multiiilaments may be spun when the humidity is less than20 grains per pound. When the humidity is above 60 grains of moistureper pound, the laments are soft and it is dii'cult to maintain spinningtension.

The spinning of the dispersion of swollen collagen fibrils to produce around bonded strand having outstanding properties wil-l be illustratedby Example `I. In Exarnpie i1, the false twister is operated in a dryatmosphere to produce an open unbonded collagen multilament.

In the examples, all quantities are expressed in parts by weight unlessotherwise indicated.

Example I A collagen dispersion, prepared as described in U.S. PatentNo. 2,919,998 is deaerated under 4vacuum for 4 hours, aged for 3l hoursat 25 C. and 16 hours at 5 C., and then spun iny the vertically upwardspinning machine illustrated in FIGURE The pressurek in the dispersionreservoir as indicated by the pressure gauge li141 is l5 pounds. Thepump 115 is operated to extrude 2.82 milliiliters of the dispersion eachminute. The pressure at lthe iilter, as `measured by the gauge 119 isapproximately 10 pounds. The spinnerette employed -may lbe a brasspla-te drilled with 40 openings arranged in three concentric circles.vThe acetone dehydrating bath is continuously circulated to the spinningcolumn at the rate of about 900 milliliters per minute.

The speed of the godets 1&1, 192 and 103 is maintained at l0, 13.5 and14 r.p.rn., respectively. The false twisters 1112 and 113` are bothrotated at 600 r.p.my. The strand vis continuously tanned at godet 102by contacting an aqueous solution containing 4 milliliters of 40%aqueous formaldehyde and 1 gram of aluminum amrnonium sulfate per liter,which solution is circulated at therate of 50V cubic centimeters perminute (25 cubic centimeter per minute through each jet). The blower`113 is `adjusted to maintain a tension of 45 to` 50* grams as indicatedby the tensiometer 142i. The blower 134 is directed above the falsetwister 1113 in a manner such that the tension indicated by thetensiometer 143 is about 190 grams. The humidity is maintained at about30 grains* of moisture per pound of dry air lthroughout the spinning.

Under these conditions, the wet tanned strand dries ou-t before thereverse twist is applied by false twister '113. Since lthe strand issubstantially dry at the point of contact with the false twister, theroundness imparted to the strand when wet is not removed.

The spinning machine operates continuously and without any difficulties,such as broken strands, under these conditions. rPhe rate of talteup atthe spool 147 is about 42 inches per minute. At the end of 6 hourscontinuous spinning, about 1300 linear feet of a round and uniformcollagen bonded strand (size 5/0, -244 denier) is collected. l

The tensile strength characteristics of this product exceed therequirements set out in the Pharmacopeia of the United States, Vol. XV,page 708.

Example II A collagen dispersion (0.86% solids) is spun in thevertically upward spinning machine illustrated in FIG- URE 1. The pump115 is operated to extrude 19.1 milliliters of the dispersion eachminute. The spinning column used has an inside diameter of 11/16 inches,and the acetone dehydrating bath -is circulated through this spinningcolumn at the rate of about 238() millilters per minute. The multilamentthat emenges from the dehydrating bath is wrapped 11/2 times around thegodet :101 and passes to the false twister 112. To avoid bonding of themultilarnent, a dry atmosphere is maintained (less than 20 grains ofmoisture per pound of dry air), and the false twister 1112 is rotated at200 r.p.m. The speed of godets 1G11 land 1012 is maintained at 10 and 13r.p.m., respectively, thus producing a stretch between godets 101 and102 of 30%. Heat is applied by the heater 133` below false twister1-1-2, and the dried multiiilament is wrapped 12 times around the godet102. From godet 102, the multilament passes directly to .the takeupspool. This multiiilarnent may be wet out, tanned, stretched, and bondedas described in Example I 4above to form a strand (size 2/0), Vthat isequivalent in all respects to cat gut manufactured from intestines.

While the description abo-ve refers specifically to the extrusion andtreatment of multiiilament, it will be recognized that a ribbon ormultiribbon may be extruded in a similar manner and process with onlyminor modications in the machine illustrated fin FGURE 1, such as usinga spinnerette with one or more slots instead of the orifices.

The addition of a bonding agent to the collagen {ilaments or ribbons isnot required because 4the individual collagen laments will adhere toeach other in the Wet stage. Bonding agents may, however, be used in thepractice of the present invention when it is desired -to manufacturewith the false twisters `a round strand of fibrils, iilaments or ribbonsthat would not adhere to each other in the absence of a bonding agent,or because of the employment of operating conditions which wouldotherwise produce only an 'incompletely bonded multifilament.

The necessity of completing the bonding step before the reverse twist isapplied will, of course, be appreciated.

While the invention has been described in detail according to thepreferred manner of carrying out the process and yielding the products,it will be obvious to those skilled in the art, Iafter understanding theinvention, that changes and modifications may be made therein withoutdeparting from the spirit or scope of the invention, and it is intendedin the appended claims to cover such changes and modilications.

The present application is a division of application Serial No. 806,067,led April 13, 1959, now abandoned.

What is claimed is:

1. In the method of manufacturing a round collagen strand of uniformcross-section throughout its length, 'the steps which include twisting amultiplicity of wet collagen monolaments to wring out excess moistureand to bond the monolaments into a unitary structure, drying themonotilaments while in the twisted condition, and removing the twist.

2. A method of bonding and rounding wet collagen ribbon to form a suturewhich comprises the steps of twisting the wet collagen ribbon to wringout excess moisture, drying the collagen ribbon while in the twistedcondition to form a bonded unitary structure of circular crosssectionand removing the twist.

3. A method of bonding `and rounding a wet collagen multilament to forma strand which comprises the steps of:

(a) twisting the collagen ymultilament in its wet state to wring outexcess moisture;

(b) `drying the collagen multililament While in the twisted condition toform a strand of circular crosssection, the filaments of which arefirmly bonded together; and,

(c) untwisting the dried collagen strand.

4. A method of manufacturing a collagen strand which comprises the stepsof:

(a) twisting wet collagen multiilament to wring out excess moisture;

(b) drying the laments while in the twisted condition; and,

(c) removing the twist.

(Corresponding to Great Britain No. 814,637, June 10, 1959)

3. A METHOD OF BONDING AND ROUNDING A WET COLLAGEN MULTIFILAMENT TO FORMA STRAND WHICH COMPRISES THE STEPS OF: (A) TWISTING THE COLLAGENMULTIFILAMENT IN ITS WET STATE TO WRING OUT EXCESS MOISTURE; (B) DRYINGTHE COLLAGEN MULTIFILAMENT WHILE IN THE TWISTED CONDITION TO FORM ASTRAND OF CIRCULAR CROSSSECTION, THE FILAMENTS OF WHICH ARE FIRMLYBONDED TOGETHER; AND, (C) UNTWISTING THE DRIED COLLAGEN STRAND.
 4. AMETHOD OF MANUFACTURING A COLLAGEN STRAND WHICH COMPRISES THE STEPS OF:(A) TWISTING WET COLLAGEN MULTIFILAMENT TO WRING OUT EXCESS MOISTURE;(B) DRYING THE FILAMENTS WHILE IN THE TWISTED CONDITION; AND, (C)REMOVING THE TWIST.